/Engine/Source/Runtime/Engine/Public/GPUSortManager.h
Expected that few will be enough, since we only need severals batches when ESortBatchProcessingOrder::KeyGenAfterPreRenderAndSortAfterPostRenderOpaque.
typedef [TArray](API\Runtime\Core\Containers\TArray)< FSortBatch, TInlineAllocator< 4 > > FSortBatchArray